Address bar Auto-Complete question

[Super Monkey Balls]

No, I'm not trying to hide the name of pr0n sites I've visited, quite the opposite.
IE seems to be forgetting URL's after a day or so yet I've got auto complete on the address bar. Is there an option that's clearing my history that I've missed somewhere? It's set at 20 days

[marcus]

Is yours set like mine below?

[Super Monkey Balls]

Forms is ticked on mine, prompt me to save passwords isn't. Otherwise the same.